The Core is a part of the Metabolic Clinical Research Unit (MCRU), which was established at NIH in 2007 as part of the first NIH Strategic Plan for Obesity Research in response to the pandemic of obesity sweeping the US and the rest of the world. Currently 1/3 of the adult US population is obese and another 1/3 are overweight. Obesity is a major cause of diabetes, cardiovascular disease, and some cancers, yet our understanding of obesity physiology is rudimentary. Since 2007, the obesity epidemic has continued unabatedthe need for rigorous and properly controlled metabolic research is even more important. At NIH, much of that research is conducted on the MCRU that consists of the 5SW-N (inpatient) unit, 5SW-S (day hospital), and 7SW-S whole room calorimeters, and uses DXA body composition scanner, and Bod Pod, exercise and activity measurements that our Core performs. Research highlights: 1. We published three papers with Dr. Kevin Halls group. The energy expenditure and body composition measures we provided were critical to answer the questions whether an isocaloric ketogenic diet directly impact 24-hr energy metabolism (a four-site metabolic chamber trial that we helped coordinate and cross-calibrate), and whether a rapid weight loss program had long term impact on the metabolic adaptation in obese subjects. We are preparing several new protocols in FY18 with Dr. Hall, addressing how highly processed food might impact energy balance, and body fat gain during carbohydrate vs. fat refeeding. 2. We published two papers with Dr. Jack Yanovskis research group. The body composition and fitness measures we provided were critical to show the effects of treatment in overweight adolescent girls at risk for type 2 diabetes. We continue our fruitful collaborations with the NICHD group on two new protocols (17-CH-0078) on Setmelanotide treatments of obesity, which is based on our previous trial of a single dose of this MC4R agonist on energy expenditure, and an extension of the sedentary break intervention trial based on our initial study in normal and obese adolescents. 3. We continue to collaborate with researchers in Icelandic and published a paper in FY17. The purpose of this study was to objectively measure, with wrist-worn actigraphy, free-living sleeping patterns in 301 Icelandic adolescents. We found that the average sleep time in these teens were only 6.2 hours per night on school days, which is far below the recommended 8 hours. The non-school days, teens compensated by getting up later by one hour. The average Icelandic teens go to bed after midnight. These findings provide information on the sleep patterns of adolescents and may serve as reference for development of policies and interventions to promote better sleep practices. 4. Our work with accelerometers has touched clinical applications in digital diabetes monitoring. We publish a paper with University of California at Santa Barbara in a study where we simultaneously measured physical activity by accelerometry and continuous glucose in 12 patients with type I diabetes during and after exercise studies. our results suggest that short duration sprints may lead to a drop in blood glucose in T1D patients, but also highlight the challenges in studying exercise in this group as the need for postexercise interventions (carbohydrate intake) is common. 5. New studies are being planned with collaborations with intramural and extramural collaborators. In FY 17, we started the intra-extramural U01 grant titled Microbial, immune, metabolic perturbations by antibiotics (MIME study) (NIH 1U01AI22285-01, PI. Martin Blaser) with investigators from NYU and NIAID. We are studying the effects of two common antibiotics a tetracycline (doxycycline) and a beta-lactam (amoxicillin) on human microbial populations and on metabolic and immune physiology in healthy volunteers in three aims: (1) the effects of a brief therapeutic course of antibiotics on microbiota and metagenome composition, (2) the effects on immune functions, and (3) the effects on metabolic physiology (24-hr metabolic chamber studies at 5 time points). We also started a study with NINDS (16-I-0078, PI, Dr. Avi Nath) under the Directors Initiative to study myalgic encephalomyelitis and chronic fatigue syndrome. We are measuring many physiological parameters, including energy expenditure and sleep (in our metabolic chambers) before and after a maximal exercise challenge. The Core currently supports 26 clinical protocols from 8 IC's of the NIH. Services rendered (FY17 activities): energy expenditure by whole-room respiratory chambers (197), resting energy expenditure by metabolic carts (303), graded-exercise tests (58), experimental food behavior tests (224), and body composition (231 DXA, 78 Bod Pod).